From 5ea5dff59780c019d67f0863c6d856d42dbf31b0 Mon Sep 17 00:00:00 2001 From: Profpatsch Date: Mon, 13 May 2024 16:02:05 +0200 Subject: feat(users/Profpatsch/MyPrelude): add Arg Change-Id: I218562c924489ff9cba783dc88ecb8e777c8aac3 Reviewed-on: https://cl.tvl.fyi/c/depot/+/11656 Reviewed-by: Profpatsch Autosubmit: Profpatsch Tested-by: BuildkiteCI --- users/Profpatsch/my-prelude/src/Arg.hs | 34 ++++++++++++++++++++++++++++++++++ 1 file changed, 34 insertions(+) create mode 100644 users/Profpatsch/my-prelude/src/Arg.hs (limited to 'users/Profpatsch/my-prelude/src/Arg.hs') diff --git a/users/Profpatsch/my-prelude/src/Arg.hs b/users/Profpatsch/my-prelude/src/Arg.hs new file mode 100644 index 0000000000..a6ffa90924 --- /dev/null +++ b/users/Profpatsch/my-prelude/src/Arg.hs @@ -0,0 +1,34 @@ +module Arg where + +import Data.String (IsString) +import GHC.Exts (IsList) +import GHC.TypeLits (Symbol) + +-- | Wrap a function argument into this helper to give it a better description for the caller without disturbing the callsite too much. +-- +-- This has instances for IsString and Num, meaning if the caller is usually a string or number literal, it should Just Work. +-- +-- e.g. +-- +-- @ +-- myFoo :: Arg "used as the name in error message" Text -> IO () +-- myFoo (Arg name) = … +-- @ +-- +-- Will display the description in the inferred type of the callsite. +-- +-- Due to IsString you can call @myFoo@ like +-- +-- @myFoo "name in error"@ +-- +-- This is mostly intended for literals, if you want to wrap arbitrary data, use @Label@. +newtype Arg (description :: Symbol) a = Arg {unArg :: a} + deriving newtype + ( Show, + Eq, + IsString, + IsList, + Num, + Monoid, + Semigroup + ) -- cgit 1.4.1